This is tricky question. When I started there were framework like YUI, Ext.js, SproutCore which were... well... complicated and locking you up. After that I fo

This is tricky question. When I started there were framework like YUI, Ext.js, SproutCore which were... well... complicated and locking you up. After that I found Backbone.js and it just clicked. Most of the code produced for it is pretty portable, as there not much of framework given to begin with. So it was very easy to start hacking with. Small size of Backbone.js comes at its own costs, like lack of memory-management. But with small apps memory management should not be a problem, and by the time it become a problem, you probably will understand issues at hands well enough, as well as will be aware of Marionette.js. Backbone.js/Marionette.js (and similar size frameworks like Mithril.js) still requires quite a lot of boilerplate code, that what react.js and higher level frameworks try to solve, each in their own way. So by that time you either find one to fit how your brain works, or find your own combination of lower level components which essentially will form your own framework, which you will understand very well by that time. That is my vision. Why I tried to warn about angular - while most of the terminology/architecture choices you learn from most client-side frameworks are very transferable to others, angular's - does not. Therefore knowing angular is important if you day job is UI engineer, since it is very popular choice, especially in corporate environment lately, I would not recommend it as very first and, especially, the only one, framework to learn. Hope this make sense :)